This invention relates to the processing of silver halide color photographic materials, and more specifically to color developer solutions containing new preservatives, or antioxidants, that improve the stability of the developer solution.
Color developers, such as, 4-amino-3-methyl-N-(.beta.-methanesulfonamidoethyl)aniline, are reducing agents, and are quite susceptible to aerial oxidation, i.e., oxidation by dissolved oxygen. To alleviate this problem, color developers generally contain an antioxidant, or preservative, to preserve the oxidation state of the color developer and maintain useful color developer activity.
Many classes of compounds have been employed as color developer solution antioxidants, e.g., hydroxylamines, hydroxamic acids, oximes, nitroxy radicals, hydrazines, hydrazides, phenols, saccharides, monoamines, diamines, tertiary amines, polyamines, quartinary ammonium salts, alpha-hydroxy ketones, alcohols, diamides, and disulfonamides. To be practical, antioxidants must be soluble in aqueous media, non-toxic to living organisms, low cost, and non-silver halide developers. Further, it is desirable that antioxidants react slowly with oxygen and rapidly with oxidized color developer, but not so rapidly that color development is retarded. These considerations greatly limit the number and class of compounds that can be used as practical antioxidants in color developer solutions.
The compounds most often employed as photographic color developer preservatives, or antioxidants, are the hydroxylamines. Hydroxylamines exhibit excellent characteristics as color developer antioxidants. Their rate of aerial oxidation is slow, they are not good silver halide developers, and they are relatively inexpensive to produce. Examples of hydroxylamines which have been used in color developers can be found in U.S. Pat. Nos. 4,978,786; 4,800,153; 4,801,516; 4,814,260; 4,965,176; 4,966,834; and 5,071,734.
Unfortunately, many hydroxylamines, both mono-and di-substituted, have significant vapor pressure at room and processing temperatures, and yield an "amine like", or unpleasant, odor. Other hydroxylamines do not meet the stability requirements for a color developer. To prolong developer activity the antioxidant must also be stable when it has undergone oxidation by oxygen, or, as a result of its preserving action, reaction with oxidized color developer. There is still a need for a hydroxylamine antioxidant which is odorless and which is stable after it undergoes oxidation.